The difference between stupidity and insanity

A medical doctor who was to attend a meeting drove his car out of his garage in a hurry because he was almost late for meeting. On his way, one of his tyres got flattered so he packed beside a psychiatric hospital to repair his flat tire. While changing the tire, all the bolt used in screwing the tyre feel into the gutter. All his effort to get the bolts proved abortive, so the doctor started pacing around talking to himself, ‘how do i get these bolts? and I’m almost late for the meeting’. ‘A man who was admitted in the psychiatric hospital was looking at the doctor and said ‘sir, should i give you a suggestion? The doctor, knowing that the man was insane, pretended as if he didn’t hear the man so he continued pacing and talking to himself. The man repeated his ‘should I give you a suggestion statement’ again and the doctor didn’t still answer him. The third time, the man said ‘sir let me help you’ but the doctor shouted at him saying ‘if you know a way out, you can say it and stop disturbing me’’. The man then said ‘’why can’t you remove one bolt each from the other 3 tyres of the vehicle and use it to screw the one you are replacing which will make all the 4 tires have 3 bolts each’’. The medical doctor, realising the sense in this, turned to the man and said ‘’but you are insane, how did you know this?’’ But the man replied ‘’I’m being kept here for ‘INSANITY and not STUPIDITY’